1. Field of the Invention
This invention relates to a single facer for forming a single-faced corrugated fiberboard by pasting a liner with a corrugating medium having flutes formed when it was passed through a gap defined between a first corrugating roll and a second corrugating roll each having wavy flutes formed on the circumference.
2. Description of the Related Art
In an apparatus for forming a single-faced corrugated fiberboard (hereinafter referred to as a single facer), a first corrugating roll and a second corrugating roll each having wavy flutes formed on the circumference are rotatably supported by frames in a vertical relationship in such a way that they may engage with each other by their flutes, and a press roll is designed to be pressed against the second corrugating roll via a corrugating medium and a liner which are webs of the single-faced corrugated fiberboard. Namely, the corrugating medium, which is fed to and between the first corrugating roll and the second corrugating roll, is allowed to have a predetermined corrugation (flutes) when it is passed between these rolls. A starchy glue is applied to the tips of flutes thus formed by a gluing roll provided in a gluing mechanism. Meanwhile, the liner being fed from the opposite side with respect to the corrugating medium via the press roll is pressed against the glued flute tips of the corrugating medium, between the press roll and the second corrugating roll, to be pasted together and form a single-faced corrugated fiberboard.
The press roll employed in the conventional single facer is of a large-diameter metallic roll which is normally urged toward the second corrugating roll so as to apply a predetermined nip pressure to the corrugating medium glued at the flute tips and the liner passing between these rolls and form a single-faced corrugated fiberboard. Since flutes consisting of alternative repetition of crests and troughs are formed continuously at a predetermined pitch on the circumference of the second corrugating roll, the distance between the rotation center of the second corrugating roll and that of the press roll shift slightly as the point of press contact of the second corrugating roll shifts from the trough to the crest or vice versa. Thus, as the result that the rotation centers of these rolls make cyclic reciprocating motions to be closer or farther relative to each other as they rotate, great vibration and big noise are generated during formation of the single-faced corrugated fiberboard, causing the working environment in the plant to be worsened considerably. Besides, such relative periodical shift of the rotation centers of these rolls causes the crests of the second corrugating roll to hit periodically the surface of the press roll to apply impact (so-called the hammering phenomenon). Accordingly, linear press marks corresponding to the pitch of the crests of the second corrugating roll are formed crosswise on the surface of the liner in the thus formed single-faced corrugated fiberboard, disadvantageously. The problems described above are brought about by the great nip pressure secured between the second corrugating roll and the press roll, which is required to nip the corrugating medium and the liner at one line contact between the second corrugating roll and the press roll opposing each other and to paste them together.